Such a device has been described, for example, in DE 33 35 743 A1. This device, however, is not suited for measurements of very high accuracy.
In recent times, measuring devices, especially slide-type gauges, have been developed further so that presently measuring pickups are available having a measurement resolution on the order of magnitude of 1/1000 mm. This means that increased attention must be devoted to the influences exerted by errors occurring during the measurement.
Linear measuring devices, such as slide-type gauges, bend under the influence of the measuring stresses and therefore are very sensitive to variations in measuring pressure. Thus, measuring accuracy is served well by maintaining the measuring pressure as constant as possible and making the measuring step as independent as possible from the sensory ability of the person performing the measuring step. In order to attain this object, solutions have been proposed as disclosed, for example, in DE 33 35 743 A1 or U.S. Pat. No. 4,873,771. Both instances involve instruments for the measurement of distances. The influence by the person doing the measurement is eliminated by the feature that, after a certain measuring pressure has been reached upon engagement of the measuring jaws, the jaws are mutually blocked so that they no longer react to outside influences.
It has been known from the measuring art that a measuring device in most cases will not as yet assume the ideal measuring position upon a first engagement; this depends, inter alia, on the manner in which the device is manipulated. It is then possible, while maintaining the measuring pressure, to bring the device into the definite measuring position by holding it more loosely, by relatively small motions or by vibrations, thus attaining accurate measuring results. However, in the aforementioned devices, such correcting steps cannot be performed since, after all, the measuring arms are blocked upon the first engagement.
It is furthermore known that slide-type gauges are poorly suited for certain, frequently occurring measuring tasks. This holds true in case of workpieces which are being machined or which are clamped in place for checking purposes.